Sikhiri River (Ordovician of Bolivia)

Where: Bolivia (17.2° S, 66.3° W: paleocoordinates 45.0° S, 126.7° W)

• coordinate estimated from map

• outcrop-level geographic resolution

When: San Benito Formation, Katian (453.0 - 445.2 Ma)

• The age of the San Benito Formation has been considered largely as Late Ordovician on the basis of its stratigraphic position below the Hirnantian/ Early Silurian Cancañiri Formation and above the Anzaldo Formation, which is significant because it yielded numerous articulated specimens of the pteraspidomorph agnathan Sacabambaspis janvieri Gagnier, Blieck and Rodrigo, 1986. Although the precise age of the Anzaldo Formation remains unclear, a late Darriwillian to early Sandbian age is accepted on the basis of its palynomorph content (Gagnier et al., 1986; Suárez Soruco, 2000; Davies et al., 2007) as well as its correlation with conodont-dated stratigraphic units of Argentina bearing microremains of Sacabambaspis (Albanesi et al., 1995; Albanesi and Astini, 2002). Unpublished palynomorphs and chitinozoans from the beds yielding the brachiopods described in this paper include Villosacapsula setosapellicula (Loeblich), Rhabdochitina cf. magna Eisenack, Ancyrochitina cf. ancyrea Eisenack and Desmochitina minor cocca Eisenack suggesting a Katian age (Pérez-Leyton, 1996).

•Overall consensus: this is basal Katian.

• group-level stratigraphic resolution

Environment/lithology: shoreface; sandstone and micaceous siltstone

• The San Benito Formation is a c. 500 m thick succession of shallow-water quartzitic sandstones with minor interbeds of dark gray micaceous siltstones. Shelly fossils have been found at few horizons and consist mainly of linguliformean brachiopods, bivalves(Suárez Soruco, 1976; Sánchez and Suárez Soruco, 1996), and a few homalonotid trilobite remains. Poorly preserved graptolites occur occasionally in the shaly beds.

Size class: macrofossils

Preservation: cast

Primary reference: J. L. Benedetto. 2013. Upper Ordovician Brachiopods from the San Benito Formation, Cordillera del Tunari, Bolivia. Ameghiniana 50(4):418-428 [P. Wagner/P. Wagner]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 167263: authorized by Pete Wagner, entered by Pete Wagner on 09.03.2015

Creative Commons license: CC BY (attribution)

Taxonomic list

unclassified
  -
Protozoa
  -
Strophomenata
 Strophomenida - Rafinesquinidae
Rhynchonellata
 Orthida - Draboviidae
Hirnantia cf. transgrediens, "Tunaria cocksi n. gen. n. sp." = Tunariorthis cardocanalis
"Tunaria cocksi n. gen. n. sp." = Tunariorthis cardocanalis Havlicek and Branisa 1980